Rock crushing devices for reducing the size of rocks or other pieces of ore or the like are well known in the prior art. Many of these rock crushing devices have been developed that use replaceable wear plates. U.S. Pat. Nos. 1,187,159 to McKee et al., 2,465,607 to Roubal and 3,153 512 to Polzin all disclose jaw crushing devices having replaceable wear plates bolted to the faces of a pivotable crushing jaw. U.S. Pat. No. 4,394,982 to Wilson discloses a grinding mill that also uses bolted wear plates. U.S. Pat. No. 4,609,158 to Wilson teaches a replaceable liner assembly for the interior shell of a grinding mill that employs a wedge element to hold a replaceable wear insert in place.
Replaceable wear plates for gyratory rock crushers have also been developed. Conventional gyratory rock crushers employ a large open, essentially conical, chamber or pit within which a main shaft rotates. A crusher mantle conforming essentially to the shape of the chamber is fixed on the main shaft for rotation within the open chamber. Material to be crushed is poured into the chamber and is ground into smaller particles between the mantle and the chamber walls as the mantle rotates. U.S. Pat. No. 3,353,758 to Whaley discloses a crusher liner that is affixed to the inner surface of the crushing chamber by a layer of relatively low melting point metal such as zinc. Wooden dowels are used to space the liners away from the chamber walls and act to absorb and distribute compressive loads. U.S. Pat. No. 4,065,064 to Anthony discloses wear resistant linings that are bolted to the inside wall of the lower portion of the chamber. Unfortunately, neither Whaley nor Anthony address the problem of the tremendous wearing forces to which the crusher mantle is subjected.
Most conventional gyratory rock crushers still do not employ replaceable wear liners. Instead, the outer surface of the mantle and the walls of the chamber have specially hardened surfaces to withstand the large abrasion forces experienced during crushing operations. Conventional rock crushers use mantles constructed from one or two piece manganese steel castings. When suitably work hardened to around 500 Brinell, these mantles provide fairly good wear life. However, to adequately work harden a manganese steel mantle and keep it work hardened means that the crusher must be continually flooded with ore. The problem with a great deal of crushers is that this necessary flooding cannot be maintained and, as a result, the manganese steel does not obtain or retain an adequate hardness level resulting in faster wear of the mantle. In addition, there is also a problem with selective wear of the mantle in that the lower portion of the mantle tends to do most of the crushing work and consequently receives most of the wear.
At present, a manganese steel mantle requires repair or replacement approximately every ten weeks. This repair process involves removing the mantle from the main shaft and building up the worn areas of the mantle by overlaying the mantle and then welding on manganese plates. Needless to say, such an operation is very labour intensive and time consuming. A mantle can be rebuilt in this manner many times, but eventually a complete replacement of the mantle is generally necessary.